A pivotal sash window adapted for installation in a master frame of a sash window assembly is well-known. The sash window assembly typically has opposed, vertically extending guide rails to enable vertical reciprocal sliding movement of the sash window in the master frame while cooperatively engaged with the guide rails or shoe channels. The sash window has a top sash rail, a base and a pair of stiles cooperatively connected together at adjacent extremities thereof to form a sash frame, usually a rectangular frame. Typically, a pair of spaced tilt-latches are installed on, or in, opposite ends of the top sash rail. Retracting a latch bolt in each tilt-latch simultaneously allows the sash window to be tilted inwardly. To this end, the sash window is pivotally supported at its base by a pair of sash balance brake shoes. The brake shoes slide within the guide rails which are typically in the form of channels.
A balance assembly is typically included with the sash window assembly to counterbalance the sash window within the master frame. One form of the balance assembly includes a spring that is connected at one end to a top portion of the master frame, typically within the shoe channel, and at another end to the brake shoe. The spring exerts an upwardly biasing force against the weight of the sash window. Different types of springs have been used in the balance assemblies. For example, a leaf spring is wound into a coil which is mounted to the guide rail and a free end of the spring is connected to the brake shoe. Some balance systems have been disclosed reversing the leaf spring configuration wherein the coiled end of the leaf spring is connected to the brake shoe and the free end is connected to the guide rail. Conventional spiral coil springs have also been used in balance systems. Block and tackle balance systems have also been utilized. These balance systems can be costly and can require large shoe channels to accommodate the balance systems.
In certain instances, the weight of the sash window requires increased counterbalance forces. Thus, multiple leaf springs have been used in tandem to increase these forces. Because windows can vary in size and weight, it can be difficult to specify a standard balance system that provides the most optimum counterbalance force against each sash window. As a result, window manufacturers must carry several different models of a balance systems having different sized springs that offer different counterbalance forces. This increases required inventories and factory space required to house all of the balance systems.
The present invention is provided to solve these and other problems.